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Valve seat feedback required

Aiki_Aviator

Well Known Member
I completed a flight yesterday and noted that I had what appeared to be a partially blocked injector on my #2 due to a significant increase in EGT to all other cylinders on approach back into my home airfield.

As such, today I completed a full injector clean and inspection.

While I was completing a bore-scope inspection I noticed what appeared to be a crack in one of the valve seats in the cylinder. I don't see any issues with the actual valve and it could well be some lead deposit and light creating the illusion of an issue, however, thought it best to post some images and get comments as what people believe the image contains and what options would then be required to pursue.

Valve top and edges look good.

170219_102925.jpg


Apparent crack.... and interesting section with a bit of oil in it.... uhhmmm... don't know.....

170219_103257.jpg


Closer look at the edge of the valve and the seat. Some lead deposited on entry to lip.

170219_112510.jpg


Any thoughts and experience is greatly appreciated as I would not want to have this progress further if an issue.
 
At 100% the image is pixelated, so it's easy to be fooled by surface irregularity. I'm finding some things look entirely different when viewed directly by the eye, as compared to the tiny camera.

The "crack" appears to be wide, i.e. suffered a loss of material, which seems unlikely. My take is ordinary combustion deposits flaking off.

In support of that idea, see the shiny stuff splattered on the valve face and combustion chamber surface? I think your diagnosis of a blocked restrictor was correct, but it was blocked at high power too. Detonation blasts chamber deposits off the surfaces, and redeposits the melted lead component in splats and little balls. Doesn't mean anything is hurt. Did you notice a CHT rise on that cylinder?
 
The second pic is difficult to decipher. In the third picture, the black spot looks like the layer of deposit broke off, not any damage to the the seat. If the third picture is the same area as the second picture, I wouldn't be too worried or at least take more pics to confirm. I struggle to come up with a scenario where a small chunk of a valve seat material outside of the seating area would break off with no other apparent damage.

Larry
 
I would certainly agree with DanH. If it were cracked down into the seat, it would begin to erode a valley in the seat at the crack. There is uncertainty about what it really is due to the camera. It is a high probability is just a crack in surface deposits.

I am a curious guy and might use a secret technique to remove the deposits on that jug and reinspect.
 
+1 for Dan

If there was a crack in the seat itself there would be Hi-pressure gas jetting through that crack and would be seen. Also if a seat cracks it will come out of the boss very quickly and you would see its loos in the pocket. The seats are press fit into the boss or pocket, when you crack one it can't hold that press fit pressure for long. It is hard to tell from a JPG but I think your looking OK here.
Yours, R.E.A. III #80888
 
At 100% the image is pixelated, so it's easy to be fooled by surface irregularity. I'm finding some things look entirely different when viewed directly by the eye, as compared to the tiny camera.

The "crack" appears to be wide, i.e. suffered a loss of material, which seems unlikely. My take is ordinary combustion deposits flaking off.

In support of that idea, see the shiny stuff splattered on the valve face and combustion chamber surface? I think your diagnosis of a blocked restrictor was correct, but it was blocked at high power too. Detonation blasts chamber deposits off the surfaces, and redeposits the melted lead component in splats and little balls. Doesn't mean anything is hurt. Did you notice a CHT rise on that cylinder?

Basically the EGT got over 1550 I believe where others were sitting at about 1430. On the CHT rise, answer was No. I got to it pretty quickly. I saw the rise and dropped power back fairly quickly so bought the EGT back down and ran rich till ground. Then made sure that I did a clean out before next flight.
 
Secret technique

I would certainly agree with DanH. If it were cracked down into the seat, it would begin to erode a valley in the seat at the crack. There is uncertainty about what it really is due to the camera. It is a high probability is just a crack in surface deposits.

I am a curious guy and might use a secret technique to remove the deposits on that jug and reinspect.

I am definitely interested in the secret technique. If you don't want to post, maybe send me a personal message ;-)
 
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